Usefulness of gray-scale contrast-enhanced ultrasonography (SonoVue®) in diagnosing hepatic alveolar echinococcosis.

Hepatic alveolar echinococcosis (HAE) is a parasitic infection with an infiltrative growth pattern that has the appearance of a hepatic malignant tumor. Ultrasound (US) has been used for screening of HAE in epidemic areas. However, it has been very difficult to evaluate the clear boundary and microvessel perfusion of the lesions. The aim of this study was to demonstrate the characteristic imaging and clinical significance of HAE lesions by contrast-enhanced ultrasonography (CEUS). Seventeen patients with 19 HAE lesions were examined in sequence with US, color Doppler flow imaging (CDFI) and then CEUS before any treatment. All the data were compared before surgery. Examined by fundamental US, 47.4% of HAE lesions showed irregular hyperechoic substantive areas and 52.6% appeared as having a mixed echotype with irregular anechoic areas in the central portion of the lesions. The CDFI method indicated no blood flow signals inside any of the 19 lesions. By CEUS, all 19 lesions displayed circular rim enhancement in the peripheral segments and absent enhancement within the central areas of the lesions (a "black hole" effect). As a result, the lesions' margins were clear, irregular and distinct. In general, the sizes of all the HAE lesions observed by CEUS were larger than those obtained by fundamental US. Therefore, CEUS is a simple imaging method and can be a helpful tool for more accurate sizing of HAE lesions and their surrounding invasion range and the proper cut-off margin when radical hepatectomy is needed.